Polyaniline coating on carbon fiber fabrics for improved hexavalent chromium removal

Carbon fabrics (CFs) loaded with 5.0, 10.0, 15.0 and 20.0 wt% polyaniline (PANI) (PANI/CF) prepared by soaking carbon fiber fabrics in 1.0 wt% PANI m-cresol solution have demonstrated superior hexavalent chromium (Cr(VI)) removal performance compared to the as-received CFs. The PANI/CF nanocomposites were noticed to remove Cr(VI) from solutions with an initial Cr(VI) concentration of 1.0 mg L-1 within 15 min, which is faster than the conventional active carbon (6 h) and the as-received CFs (>1 h). A better Cr(VI) removal efficiency was observed in the acidic solutions than in the basic solutions. A pseudo-second-order behavior was justified for the PANI/CF with a much higher removal rate (0.06 g mg(-1) min(-1)) than the reported similar to 0.03 g mg(-1) min(-1) for the active carbon. The adsorption isotherm study demonstrated that the adsorbents follow the Langmuir model with a calculated maximum adsorption capacity of 18.1 mg g(-1) for the 10.0 wt% PANI/CF. The Cr(VI) removal mechanisms explored by FT-IR and XPS involve the reduction of Cr(VI) to Cr(III) by PANI. The PANI/CF adsorbents have demonstrated easy recycling capability for up to five cycles with a Cr(VI) removal rate at above 91%.